This invention relates to conveyor elements for the transport of bulk materials such as coal and the like, and which may often include a belt having a U-shaped upper reach that defines an elongated pocket which is able to negotiate turns in a horizontal direction during traverse of an elongated, generally curvilinear conveying run. Prior conveyor elements of this type have employed such means as centrally located cables to carry the required driving tension, and the belt structure has often included a web of resiliently deformable material which is able to accommodate elongation or shortening of the belt, and particularly of the belt edges, in horizontal turns whereby the problem of belt edge collapse in horizontal turns has been alleviated. For example, molded edge flutes have been employed in such belts to fold or unfold as required in horizontal turns.
In copending application Ser. No. 06/069,664 of Merle L. Hoover, filed Aug. 24, 1979, which is now abandoned and continued as U.S. application Ser. No. 224,419, filed on Jan. 12, 1981 which will issue into U.S. Pat. No. 4,387,801 on June 14, 1983, is assigned to the same assignee as is the instant invention and the entire specification of which is incorporated herein by reference, a conveyor element is disclosed which negotiates horizontal turns without collapse of the belt edges by virtue of a limited prestretch imposed on the belt at installation thereof in the conveyor support structure such that the belt edges remain in longitudinal tension when the belt passes through horizontal turns. In one embodiment thereof the prestretching of this belt is achieved by riveting or otherwise fastening the resiliently deformable belt to a chain which has a predetermined freeplay in the link connections to permit the chain to elongate and thereby prestretch the belt. That is, when the chain is attached to the conveyor belt during assembly, the chain links are in effect pushed together such that upon installation of the chain and belt assembly in the support structure the belt may be resiliently stretched to the extent permitted by the loose pin connections of the chain links to impose a predetermined prestretch over and above the relaxed or unstretched length of the belt.
In U.S. Pat. No. 4,282,971 of Henry R. Becker, issued Aug. 11, 1981 which is assigned to the same assignee as is the instant invention and the specification of which is incorporated herein by reference, an expansible chain for conveyor belts is disclosed which is formed of alternate links, one being a C-shaped link secured to a conveyor belt and the other being a floating H-shaped connecting link which connects adjacent C-links together but is not itself directly secured to the belt, and which is adapted to be engaged by a drive sprocket. The structure of the H- and C-links is such as to permit a limited free play in the connections therebetween such that the links may be loosely fitted together upon assembly thereof to a resiliently deformable belt and thus upon installation of the belt in its support structure the chain will permit a limited and predeterminable prestretching of the belt to the limit of chain expansion as hereinabove described.